Benzoxazine-thiol adducts

ABSTRACT

Novel benzoxazine-thiol adducts are described, which may be may be cured to produce compositions useful in coating, sealants, adhesive and many other applications.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication No. 61/184,328, filed Jun. 5, 2009, the disclosure of whichis incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present disclosure is directed to novel compounds and polymersderived from the reaction of benzoxazine compounds with thiol compounds.The compositions are useful in coating, sealants, adhesive and manyother applications.

BACKGROUND

Benzoxazines and compositions containing benzoxazine are known (see forexample, U.S. Pat. Nos. 5,543,516 and 6,207,786 to Ishida, et al.; S.Rimdusit and H. Ishida, “Development of New Class of ElectronicPackaging Materials Based on Ternary Systems of Benzoxazine, Epoxy, andPhenolic Resins”, Polymer, 41, 7941-49 (2000); and H. Kimura, et al.,“New Thermosetting Resin from Bisphenol A-based Benzoxazine andBisoxazoline”, J. App. Polym. Sci., 72, 1551-58 (1999).

U.S. Pat. No. 7,517,925 (Dershem et al.) describes benzoxazine compoundsand thermosetting resin compositions prepared therefrom. Thecompositions are said to be useful for increasing adhesion at interfaceswithin microelectronic packages and low shrinkage on cure and lowcoefficient of thermal expansion (CTE).

U.S. Pat. No. 7,053,138 (Magendie et al.) describes compositionscomprising benzoxazines and thermoplastic or thermoset resins in themanufacture of prepregs and laminates. The compositions are said toyield flame-proofed laminating resins that have high glass transitiontemperatures.

U.S. Pat. No. 6,376,080 (Gallo) describes a method of preparing apolybenzoxazine which includes heating a molding composition including abenzoxazine and a heterocyclic dicarboxylic acid to a temperaturesufficient to cure the molding composition, thereby forming thepolybenzoxazine. The compositions are said to have near-zero volumechange after post cure.

SUMMARY

The present disclosure is directed to novel benzoxazine-thiol adducts.Further, the present disclosure is directed to a method of preparing theadducts, which comprises reacting a benzoxazine compound with a thiolcompound, the reaction resulting in ring-opening of the oxazine ring,and resulting in an sulfanylmethyl aminophenolic compound. The presentbenzoxazine-thiol adducts may be cured to produce cured compositionsuseful in coating, sealants, adhesive and many other applications. Thepresent disclosure further provides a curable composition comprising abenzoxazine compound and a thiol compound, which when cured is useful inadhesive, coating and bonding applications.

In the process of preparing the benzoxazine-thiol adducts, each of thestarting materials may be mono- or higher functionality. The benzoxazinemay be a mono- or higher benzoxazine, and the thiol compound may be amono- or higher thiol.

As used herein the term “benzoxazine” is inclusive of compounds andpolymers having the characteristic benzoxazine ring. In the illustratedbenzoxazine group, R is the residue of a mono- or polyamine.

As used herein, “alkyl” includes straight-chained, branched, and cyclicalkyl groups and includes both unsubstituted and substituted alkylgroups. Unless otherwise indicated, the alkyl groups typically containfrom 1 to 20 carbon atoms. Examples of “alkyl” as used herein include,but are not limited to, methyl, ethyl, n-propyl, n-butyl, n-pentyl,isobutyl, t-butyl, isopropyl, n-octyl, n-heptyl, ethylhexyl,cyclopentyl, cyclohexyl, cycloheptyl, adamantyl, and norbornyl. and thelike. Unless otherwise noted, alkyl groups may be mono- or polyvalent.

As used herein, the term “heteroalkyl” includes both straight-chained,branched, and cyclic alkyl groups with one or more heteroatomsindependently selected from S, O, and N both unsubstituted andsubstituted alkyl groups. Unless otherwise indicated, the heteroalkylgroups typically contain from 1 to 20 carbon atoms. “Heteroalkyl” is asubset of “hetero(hetero)hydrocarbyl” described below. Examples of“heteroalkyl” as used herein include, but are not limited to methoxy,ethoxy, propoxy, 3,6-dioxaheptyl, 3-(trimethylsilyl)-propyl,4-dimethylaminobutanyl, and the like. Unless otherwise noted,heteroalkyl groups may be mono- or polyvalent.

As used herein, “aryl” is an aromatic group containing 6-18 ring atomsand can contain fused rings, which may be saturated, unsaturated, oraromatic. Examples of an aryl group include phenyl, naphthyl, biphenyl,phenanthryl, and anthracyl. Heteroaryl is aryl containing 1-3heteroatoms such as nitrogen, oxygen, or sulfur and can contain fusedrings. Some examples of heteroaryl are pyridyl, furanyl, pyrrolyl,thienyl, thiazolyl, oxazolyl, imidazolyl, indolyl, benzofuranyl, andbenzthiazolyl. Unless otherwise noted, aryl and heteroaryl groups may bemono- or polyvalent.

As used herein “(hetero)hydrocarbyl” is inclusive of (hetero)hydrocarbylalkyl and aryl groups, and hetero(hetero)hydrocarbyl heteroalkyl andheteroaryl groups, the later comprising one or more catenary oxygenheteroatoms such as ether or amino groups. (Hetero)hydrocarbyl mayoptionally contain one or more catenary (in-chain) functional groupsincluding ester, amide, urea, urethane and carbonate functional groups.Unless otherwise indicated, the non-polymeric (hetero)hydrocarbyl groupstypically contain from 1 to 60 carbon atoms. Some examples of such(hetero)hydrocarbyls as used herein include, but are not limited tomethoxy, ethoxy, propoxy, 4-diphenylaminobutyl,2-(2′-phenoxyethoxy)ethyl, 3,6-dioxaheptyl, 3,6-dioxahexyl-6-phenyl, inaddition to those described for “alkyl”, “heteroalkyl”, “aryl” and“heteroaryl” supra.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a plot of the dynamic mechanical analysis scans of Example 11.

DETAILED DESCRIPTION

The present disclosure is directed to novel benzoxazine-thiol adducts.The benzoxazine-thiol adducts may be described sulfanylmethylaminophenolic compounds, which may be monomeric, oligomeric orpolymeric. Such compounds are prepared by the reaction of a benzoxazinewith a thiol compound. The adducts are characterized as having thecharacteristic group resulting from ring opening of the oxazine ringwith a thiol group. In the illustrated benzoxazine group, R⁵ is theresidue of a mono- or polyamine and R⁴ is the residue of a mono- orpolythiol, and R¹ is the residue of an aldehyde.

whereineach R¹ is H or an alkyl group, and is the residue of an aliphaticaldehyde,R² is H, a covalent bond, or a polyvalent (hetero)hydrocarbyl group,preferably H, a covalent bond or a divalent alkyl group;R⁴ is the (hetero)hydrocarbyl residue of a thiol compound;R⁵ is the (hetero)hydrocarbyl residue of a primary amino compound, whichmay be a mono- or polyamine.

As used herein the term “residue” is used to define that(hetero)hydrocarbyl portion of a group remaining after removal (orreaction) of the attached functional groups, or the attached groups in adepicted formula. For example, the “residue” of butyraldehyde, C₄H₉—CHOis the monovalent alkyl C₄H₉—. The residue of hexamethylene diamine,H₂N—C₆H₁₂—NH₂ is the divalent alkyl —C₆H₁₂—. The residue of phenylenediamine H₂N—C₆H₄—NH₂, is the divalent aryl —C₆H₄—. The residue ofdiamino-polyethylene glycol, H₂N—(C₂H₄O)₁₋₂₀—C₂H₄—NH₂, is the divalent(hetero)hydrocarbyl polyethylene glycol —(C₂H₄O)₁₋₂₀—C₂H₄—.

In the preparation of the benzoxazine-thiol adducts, any benzoxazinecompound may be used. Benzoxazines may be prepared by combining aphenolic compound, and aliphatic aldehyde, and a primary amine compound.U.S. Pat. No. 5,543,516 (Ishida), hereby incorporated by reference,describes a solventless method of forming benzoxazines. U.S. Pat. No.7,041,772 (Aizawa et al.) describes a process for producing abenzoxazine resin which comprises the steps of reacting a phenolcompound, an aldehyde compound and a primary amine in the presence of anorganic solvent to synthesize a benzoxazine resin and removing generatedcondensation water and the organic solvent from a system under heatingand a reduced pressure. Other suitable reaction schemes to producemono-, di- and higher-functional benzoxazines are described in N. N.Ghosh et al., Polybenzoxazine-new high performance thermosetting resins:synthesis and properties, Prog. Polym. Sci. 32 (2007), pp. 1344-1391.One suitable method of producing the starting benzoxazine compounds isillustrated by the following reaction scheme:

whereineach R¹ is H or an alkyl group, and is the residue of an aliphaticaldehyde,R² is H, a covalent bond, or a polyvalent (hetero)hydrocarbyl group,preferably H, a covalent bond or a divalent alkyl group;R⁵ is the (hetero)hydrocarbyl residue of a primary amino compound,R⁵(NH₂)_(m), where m is 1-4; andx is at least 1.

A monophenol is illustrated for simplicity. Mono- or polyphenoliccompounds may be used. The phenolic compound may be further substitutedwithout limitation is desired. For example, the 3, 4, and 5 positions ofthe phenolic compound may be hydrogen or substituted with other suitablesubstituents such as alkyl, cycloalkyl, heterocycloalkyl, aryl,heteroaryl, aralkyl, heteroaralkyl, alkoxy, alkoxyalkylene,hydroxylalkyl, hydroxyl, haloalkyl, carboxyl, halo, amino, aminoalkyl,alkylcarbonyloxy, alkyloxycarbonyl, alkylcarbonyl, alkylcarbonylamino,aminocarbonyl, alkylsulfonylamino, aminosulfonyl, sulfonic acid, oralkylsulfonyl. Desirably at least one of the positions ortho to thehydroxyl group is unsubstituted to facilitate benzoxazine ringformation.

The aryl ring of the phenolic compound may be a phenyl ring as depicted,or may be selected from naphthyl, biphenyl, phenanthryl, and anthracyl.The aryl ring of the phenolic compound may further comprise a heteroarylring containing 1-3 heteroatoms such as nitrogen, oxygen, or sulfur andcan contain fused rings. Some examples of heteroaryl are pyridyl,furanyl, pyrrolyl, thienyl, thiazolyl, oxazolyl, imidazolyl, indolyl,benzofuranyl, and benzthiazolyl.

Examples or mono-functional phenols include phenol; cresol;2-bromo-4-methylphenol; 2-allyphenol; 4-aminophenol; and the like.Examples of difunctional phenols (polyphenolic compounds) includephenolphthalein; biphenol, 4-4′-methylene-di-phenol;4-4′-dihydroxybenzophenone; bisphenol-A; 1,8-dihydroxyanthraquinone;1,6-dihydroxnaphthalene; 2,2′-dihydroxyazobenzene; resorcinol; fluorenebisphenol; and the like. Examples of trifunctional phenols comprise1,3,5-trihydroxy benzene and the like.

With respect to the R² group of Formula II, numerous phenolic compoundsare contemplated. R² may be an H, a covalent bond “—” which represents abiphenyl-type phenolic compounds, or R² may be a divalent aliphaticgroup linking aryl rings. For example, R² may be a divalent isopropylgroup, derived from bisphenol-A, generally illustrated as follows:

whereeach R¹ is H or an alkyl group, and is the residue of an aliphaticaldehyde,R² is H, a covalent bond, or a polyvalent (hetero)hydrocarbyl group,preferably H, a covalent bond or a divalent alkyl group;R⁴ is the (hetero)hydrocarbyl residue of a thiol compound;R⁵ is the (hetero)hydrocarbyl residue of a primary amino compound.

Note that Scheme III, and other schemes herein, the product depicts freethiol groups. The depiction is used to account for all the thiol groupspresent in the starting materials, which are available for subsequentreaction. Thus the starting bis-benzoxazine reacts with the polythiolR⁴(SH)_(n), and the initial reaction product has “n−1” thiol groups,which may be available for further reaction with additional benzoxazinegroups. Further, the starting benzoxazine was prepared for a polyamine,therefore R⁵ groups may be connected to additional benzoxazine groups.

Note that in the above reaction scheme, monoamines and monothiols aredepicted, however higher functional thiols and amines may also be used.It will be understood that the reaction of polybenzoxazines with apolythiol can provide polymeric materials such as:

whereeach R¹ is H or an alkyl group, and is the residue of an aliphaticaldehyde,R² is H, a covalent bond, or a polyvalent (hetero)hydrocarbyl group,preferably H, a covalent bond or a divalent alkyl group;R⁴ is the (hetero)hydrocarbyl residue of a thiol compound;R⁵ is the (hetero)hydrocarbyl residue of a primary amino compound, andp is at least one, preferably two or more.

The aldehyde reactants used in preparing the benzoxazine startingmaterials include formaldehyde; paraformaldehyde; polyoxymethylene; aswell as aldehydes having the general formula R¹CHO, where R¹ is H or analkyl group, including mixtures of such aldehydes, desirably having from1 to 12 carbon atoms. The R¹ group may be linear or branched, cyclic oracyclic, saturated or unsaturated, or combinations thereof. Other usefulaldehydes include crotonaldehyde; acetaldehyde; propionaldehyde;butyraldehyde; and heptaldehyde.

Amino compounds useful in preparing the starting benzoxazine can besubstituted or unsubstituted, mono-, di-substituted or higher(hetero)hydrocarbyl amines having at least one primary amine group. Theamines may be aliphatic or aromatic amines. It can be substituted, forexample, with groups such as alkyl, cycloalkyl, heterocycloalkyl, aryl,heteroaryl, aralkyl, or heteroaralkyl. It has been observed thatbenzoxazines derived from aromatic amines, such as aniline, are lessreactive toward the thiol reactants than benzoxazines derived fromaliphatic amines as indicated, for example by the corresponding reactiontemperatures, as illustrated in Example 13.

Amines useful in the preparation of the starting benzoxazine compoundsinclude those of the formula R⁵(NH₂)_(m) include (hetero)hydrocarbylmonoamines and polyamines. R⁵ may be (hetero)hydrocarbyl group that hasa valence of m, and is the residue of a mono-, di- or higher aminehaving at least one primary amine group. R⁵ can be an alkyl, acycloalkyl or aryl and m 1 to 4. The R⁵ is preferably selected frommono- and polyvalent (hetero)hydrocarbyl (i.e., alkyl and aryl compoundshaving 1 to 30 carbon atoms, or alternatively (hetero)hydrocarbylincluding heteroalkyl and heteroaryl having 1 to twenty heteroatoms ofoxygen.

In one embodiment, R⁵ comprises a non-polymeric aliphatic,cycloaliphatic, aromatic or alkyl-substituted aromatic moiety havingfrom 1 to 30 carbon atoms. In another embodiment, R⁵ comprises apolymeric polyoxyalkylene, polyester, polyolefin, poly(meth)acrylate,polystyrene or polysiloxane polymer having pendent or terminal reactive—NH₂ groups. Useful polymers include, for example, amine-terminatedoligo- and poly-(diaryl)siloxanes and (dialkyl)siloxane amino terminatedpolyethylenes or polypropylenes, and amino terminated poly(alkyleneoxides).

Any primary amine may be employed. Useful monoamines include, forexample, methyl-, ethyl-, propyl-, hexyl-, octyl, dodecyl-, dimethyl-,methyl ethyl-, and aniline. The term “di-, or polyamine,” refers toorganic compounds containing at least two primary amine groups.Aliphatic, aromatic, cycloaliphatic, and oligomeric di- and polyaminesall are considered useful in the practice of the invention.Representative of the classes of useful di- or polyamines are4,4′-methylene dianiline,3,9-bis-(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5,5]undecane, andpolyoxyethylenediamine. Useful diamines includeN-methyl-1,3-propanediamine; N-ethyl-1,2-ethanediamine;2-(2-aminoethylamino)ethanol; pentaethylenehexaamine; ethylenediamine;N-methylethanolamine; and 1,3-propanediamine.

Examples of useful polyamines include polyamines having at least threeamino groups, wherein at least one of the three amino groups areprimary, and the remaining may be primary, secondary, or a combinationthereof. Examples include H₂N(CH₂CH₂NH)₁₋₁₀H, H₂N(CH₂CH₂CH₂CH₂NH)₁₋₁₀H,H₂N(CH₂CH₂CH₂CH₂CH₂CH₂NH)₁₋₁₀H, H₂N(CH₂)₃NHCH₂CH═CHCH₂NH(CH₂)₃NH.₂,H₂N(CH₂)₄NH(CH₂)₃NH₂, H₂N(CH2)₃NH(CH₂)₄NH(CH₂)₃NH₂,H₂N(CH₂)₃NH(CH₂)2NH(CH₂)₃NH₂, H₂N(CH₂)₂NH(CH₂)₃NH(CH₂)₂NH₂,H₂N(CH₂)₃NH(CH₂)₂NH₂, C₆H₅NH(CH₂)₂NH(CH₂)₂NH₂, and N(CH₂CH₂NH₂)₃, andpolymeric polyamines such as linear or branched (including dendrimers)homopolymers and copolymers of ethyleneimine (i.e., aziridine). Manysuch compounds can be obtained, or are available, from general chemicalsuppliers such as, for example, Aldrich Chemical Company, Milwaukee,Wis. or Pfaltz and Bauer, Inc., Waterbury, Conn.

Many di- and polyamines, such as those just named, are availablecommercially, for example, those available from Huntsman Chemical,Houston, Tex. The most preferred di- or polyamines include aliphatic di-and triamines or aliphatic di- or polyamines and more specificallycompounds with two or three primary amino groups, such as ethylenediamine, hexamethylene diamine, dodecanediamine, and the like.

Other useful amines include amino acids such as glycine, alanine, andleucine and their methyl esters, aminoalcohols such as ethanolamine,3-aminopropanol, and 4-aminobutanol, polyaminoethers containing ethyleneglycol and diethylene glycol (such as Jeffamine™ diamines), and alkenylamines such as diallylamine and allylmethylamine.

It will be understood that monoamines will cyclize with the aldehyde andphenolic compound to produce mono-benzoxazine compounds, while di- orhigher amines will cyclize to produce di- and poly-benzoxazinecompounds: For example, a diamine (m=2 in the Scheme below) will producea di-benzoxazine.

wherein each R¹ is H or an alkyl group, and is the residue of analiphatic aldehyde;R² is H, a covalent bond, or a polyvalent (hetero)hydrocarbyl group,preferably H, a covalent bond or a divalent alkyl group;R⁵ is the (hetero)hydrocarbyl residue of a primary amino compound.

Further, polymeric benzoxazines may be prepared from a polyphenoliccompound, such as bisphenol-A, and a di- or polyamine. Thesepolybenzoxazines may be ring-opened with a thiol compound, as previousdescribed

whereineach R¹ is H or an alkyl group, and is the residue of an aliphaticaldehyde,R² is H, a covalent bond, or a polyvalent (hetero)hydrocarbyl group,preferably H, a covalent bond or a divalent alkyl group;R⁴ is the (hetero)hydrocarbyl residue of a thiol compound;R⁵ is the (hetero)hydrocarbyl residue of a primary amino compound;z is at least 1, preferably 2 or greater.

The benzoxazine ring is opened with thiols of the formula R⁴—(SH)_(n),where n is 1 to 6. R⁴ includes any (hetero)hydrocarbyl groups, includingaliphatic and aromatic monothiols and polythiols. R⁴ may optionallyfurther include one or more functional groups including hydroxyl, acid,ester, cyano, urea, urethane and ether groups.

In some preferred embodiments, the thiol compounds are of the formula:R⁶—[(CO₂)_(x)—R⁷—SH]_(y),  IXwhere R⁶ is an alkylene group, an aryl group, an oxyalkylene group, orcombination thereof,R⁷ is a divalent hydrocarbyl group, x is 0 or 1,y is 1 to 6.

-   -   Useful thiol compounds falling within the scope of Formula IX        include thiols is of the formulas:

-   -   wherein    -   R⁶ is an alkylene group, an aryl group, an oxyalkylene group, or        combination thereof,    -   R⁷ is a divalent hydrocarbyl group,    -   x is 0 or 1,    -   y is 1 to 6. Preferably the compounds of Formulas IX to XII are        those in which R⁶ is an alkylene group.

Useful alkyl thiols include methyl, ethyl and butyl thiol, as well as2-mercaptoethanol, 3-mercapto-1,2-propanediol, 4-mercaptobutanol,mercaptoundecanol, 2-mercaptoethylamine, 2,3-dimercaptopropanol,3-mercaptopropyltrimethoxysilane, mercaptoalkanoic acids and estersthereof including mercaptoproionic acid, 2-chloroethanethiol,2-amino-3-mercaptopropionic acid, dodecyl mercaptan, thiophenol,2-mercaptoethyl ether, and pentaerythritol tetrathioglycolate. Specificexamples of useful polythiols include dimercaptodiethyl sulfide;1,6-hexanedithiol; 1,8-dimercapto-3,6-dithiaoctane;propane-1,2,3-trithiol;1,2-bis[(2-mercaptoethyl)thio]-3-mercaptopropane;tetrakis(7-mercapto-2,5-dithiaheptyl)methane; and trithiocyanuric acid.

Another useful class of polythiols includes those obtained byesterification of a polyol with a terminally thiol-substitutedcarboxylic acid (or derivative thereof such as esters or acyl halides)including α- or β-mercaptocarboxylic acids such as thioglycolic acid orβ-mercaptopropionic acid or esters thereof. Useful examples of compoundsthus obtained include ethylene glycol bis(thioglycolate),pentaerythritol tetrakis(3-mercaptopropionate), ethylene glycolbis(3-mercaptopropionate), trimethylolpropane tris(thioglycolate),trimethylolpropane tris(3-mercaptopropionate), pentaerythritoltetrakis(thioglycolate) pentaerythritol tetrakis(3-mercaptopropionate),all of which are commercially available. A specific example of apreferred polymeric polythiol is polypropylene ether glycolbis(3-mercaptopropionate) which is prepared from polypropylene-etherglycol (e.g. Pluracol™ P201, BASF Wyandotte Chemical Corp.) and3-mercaptopropionic acid by esterification.

In some embodiments, useful thiols include those thiols derived fromepoxy compounds. The polythiol may be derived from the reaction betweenH2S (or equivalent) and an epoxy resin having two or more functionalgroups and preferably having a molecular weight of less than 1000. Forexample, bifunctional epoxy resins, such as a bisphenol A epoxy resinand a bisphenol F epoxy resin, and novolak epoxy resins, such as aphenolic novolak epoxy resin and a cresol novolak epoxy resin, or amineepoxy resins, can be used. In addition, generally known polyfunctionalepoxy resins, heterocycle-containing epoxy resins, and alicyclic epoxyresins can be used. These epoxy resins may be used alone or incombinations of two or more chemical types or molecular weight ranges.

A particularly useful polythiol is that derived from bisphenol-Adiglycidyl ether, available as QX-11 from Japan Epoxy Resins, having athiol equivalent weight of ˜245 and the following general structure,where n is at least 1:

Useful soluble, high molecular weight thiols include polyethylene glycoldi(2-mercaptoacetate), LP-3™ resins supplied by LP North America.(Houston, Tex.), and Permapol P3™ resins supplied by Products Research &Chemical Corp. (Glendale, Calif.) and compounds such as the adduct of2-mercaptoethylamine and caprolactam.

As will be apparent to one skilled in the art, higher sulfanylmethylaminophenolic compounds may be prepared using polythiols:

whereeach R¹ is H or an alkyl group, and is the residue of an aliphaticaldehyde,R² is H, a covalent bond, or a polyvalent (hetero)hydrocarbyl group,preferably H, a covalent bond or a divalent alkyl group;R⁴ is the (hetero)hydrocarbyl residue of a polythiol compound;R⁵ is the (hetero)hydrocarbyl residue of a primary amino compound.

The compounds of Formula II may be prepared by combining the benzoxazinecompounds and the thiol compounds neat or in a suitable solvent.Suitable solvents include those in which the reactants dissolve,preferably at room temperature. Solvents may include that isnon-reactive with the reactants and that provides for the subsequentdissolution of co-reactants. Examples of suitable solvents include butylacetate, toluene, xylene, tetrahydrofuran, ethylene glycol dimethylether and the like. Heating is generally unnecessary as thethiol-induced ring opening is exothermic.

The stoichiometry of the reactants is not critical. Generally any molarratio of benzoxazine to thiol may be used. Generally the molar amountsratio of benzoxazine groups to thiol groups is about 1.1:1 to 1:1.1. Insome embodiments it is preferable to have an excess of benzoxazine, asan unreacted benzoxazine will homopolymerize to form a coextensivemixture or polymer network of benzoxazine-thiol adduct andpolybenzoxazines. In such embodiments, the molar amounts ratio ofbenzoxazine groups to thiol groups is about 1.1:1 to 50:1

If desired an acid catalyst may be used to promote the ring-opening ofthe benzoxazine. Suitable acid catalysts include, but are not limitedto: strong inorganic acids such as hydrochloric acid, sulfuric acid,phosphoric acid, and the like; and organic acids such as acetic acid,para-toluene sulfonic acid, and oxalic acid. Acid catalysts may be usedin amounts of 2 wt. % or less, preferably 1 wt. % or less, mostpreferably 0.5 wt. % or less, relative to the amounts of benzoxazine andthiol reactants.

The compositions may be used as coatings, including hard surfacecoatings, and pattern coatings; as adhesives, including pressuresensitive adhesives and structural adhesives; as sealants; and ascoatings for electronics and other substrates. When uncured or partiallycured, the benzoxazine compositions exhibit pressure-sensitive adhesiveproperties, including tack. In some embodiments, the present disclosureprovides a coated article comprising a substrate, having a cured coatingof the benzoxazine-thiol adduct thereon.

In some embodiments, the present disclosure provides “B-stagable”adhesives. Processing applications such as printed circuit manufactureoften employ “stageable” adhesives, that is, adhesive compositions whichcan be partially cured to a tacky or tack-free coating, fastened to anadherend, and cured using heat, pressure, or both (see. U.S. Pat. No.4,118,377). The tack-free state is sometimes referred to as the“B-Stage”. Under ASTM Standard D907-91b “B-stage” means an intermediatestage in a thermosetting resin reaction in which the material softenswhen heated, and swells, but does not dissolve in certain liquids.

The present disclosure provides stagable adhesive compositionscomprising a blend or mixture of thiol compound, benzoxazine compoundsderived from an aromatic amine and benzoxazine compounds derived from analiphatic amine. The stagable adhesive composition may further comprisean acid catalyst, as previously described. The stagable adhesivecomposition may be coated on to an adherend or substrate, and fullycured to a structural or semistructural adhesive using heat.

Upon combining the components the thiol compounds will preferentiallyreact with the benzoxazine derived from an aliphatic amine to form apartially cured mixture. This partially cured mixture may be tacky ornon-tacky at room temperature. On heating, the benzoxazine derived froman aromatic amine will react with the remaining thiol compounds toproduce a fully cured adhesive.

The physical properties (e.g. viscosity, tack, peel, shear) of theuncured, B-staged, and cured compositions to be readily altered throughthe use of different amounts of each component: the thiol, thebenzoxazine compounds derived from an aromatic amine and benzoxazinecompounds derived from an aliphatic amine, or through the use ofdifferent species of the three components.

In some embodiments, the partially cured, stagable adhesive compositionmay be disposed between two substrates (or adherends), and subsequentlyheated to fully cure the adhesive and effect a structural orsemistructual bond between the substrates. In other embodiments, thestagable adhesive composition may be heated to a flowable viscosity toeffect coating of a substrate, which may then be joined to a secondsubstrate while still molten and full curing effected.

In some embodiments, the present disclosure provides a method ofassembling components using a thermally B-staged, further thermallycurable, benzoxazine-based adhesive. In some embodiments, the thermalB-stage is accomplished by mild heating to promote partial reaction ofthe components of the stagable adhesive such that the viscosityincreases sufficiently to allow coating. The thermal B-stage is followedby a thermal cure at a higher temperature. In some embodiments, thecompositions of the present disclosure are useful for rapid assembly.The compositions of the present disclosure are particularly useful inassembly operations in which the adhesive desirably is colored or evenopaque to a degree which would be difficult to attain in a system whichis B-staged photochemically, for example by UV radiation, where thematerials to be joined are opaque, or in which the required adhesivethickness is too great for easy photochemical curing.

“Mild heating” refers to heating the composition to a first temperaturewhich is sufficient to initiate a chemical reaction between the adhesivecomponents (in particular the benzoxazine derived from the aliphaticamine) to effect a combination of reaction to increase the viscosity ofthe composition to a desirable level for the B-stage. In someembodiments, the first temperature may be at or below 0° C. In someembodiments, the first temperature will be selected to be high enough toprevent premature viscosity increases prior to application to asubstrate. In some embodiments, it may be desirable to store theadhesive composition at or below about 0° C. In other embodiments itwould be protect the adhesive composition from exposure to temperaturesabove about 80° C. prior to application to the substrate. The firsttemperature will be lower than a second, higher temperature which isnecessary to significantly initiate a secondary reaction between theadhesive components, i.e. the reaction of the thiol compound with thebenzoxazine derived from an aromatic amine. In some embodiments, thetemperature at which the adhesive composition is B-staged will begreater than about 90° C. In other embodiments, the temperature at whichthe adhesive composition is B-staged will be less than about 120° C.

It will be appreciated by those of skill in the art that the specifictemperatures associated with the terms “first temperature” and “second,higher temperature” will, of necessity, depend upon the chemicalcomponents of a specific embodiment of the compositions of the inventionand the properties of the materials to be bonded or adhered by thecomposition, the difference between the first, lower temperature and thesecond, higher temperature will generally be such that exposure to thefirst temperature is sufficient to produce the B-stage adhesive withoutsignificant advancement of the final cure mechanism or mechanisms. Insome embodiments, the difference between the first temperature and thesecond, higher temperature will be at least about 25° C., preferably atleast about 30° C. In other embodiments, the difference between thefirst temperature and the second, higher temperature will be no morethan about 50° C., preferably no more than about 40° C. If thedifference between the first, lower temperature and the second, highertemperature is too small, it may be difficult to limit the onset of thehigher temperature cure reaction or reactions. If the difference betweenthe first, lower temperature and the second, higher temperature is toolarge, the energy demands of the overall process may be undesirably highand damage to one or both of the materials to be joined may result. Insome embodiments, the second, higher temperature will be greater thanabout 115° C., preferably greater than about 130° C. In otherembodiments, the second, higher temperature will be no greater thanabout 150° C., preferably no greater than about 140° C.

In some preferred embodiments, the final thermal cure mechanism is arelatively slow reaction at the first temperature compared to theB-staging reaction that initially increases the viscosity of the resin.The relatively slower kinetics of this mechanism allow the same generictriggering event, heating, to initiate both reactions so that theadhesive composition is B-staged and tacky almost immediately afterinitial heating to a first temperature, but which does not fully cureuntil a later time at a second, higher temperature, allowing time forthe substrate and adherent to be properly aligned before curing iscomplete. In some embodiments, the B-staged composition preferably istacky enough to hold the substrate and adherent in place during thethermal cure without requiring known additional clamping means. In someembodiments, a final thermal cure at a second, higher temperature takesat least about 0.1 hours, preferably at least about 0.25 hour. In otherembodiments, the final thermal cure requires no more than about 0.75hours at the second, higher temperature, preferably no more than about1.5 hours, to complete, allowing adequate time after initial heating toensure that there is adequate contact between the adhesive composition,the substrate, and the adherent. In some embodiments, longer finalthermal cure times at lower second, higher temperatures may beacceptable or even desirable.

Therefore the present disclosure provides stagable, structural andsemi-structural adhesives. “Semi-structural adhesives” are those curedadhesives that have an overlap shear strength of at least about 0.5 MPa,more preferably at least about 1.0 MPa, and most preferably at leastabout 1.5 MPa. Those cured adhesives having particularly high overlapshear strength, however, are referred to as structural adhesives.“Structural adhesives” are those cured adhesives that have an overlapshear strength of at least about 3.5 MPa, more preferably at least about5 MPa, and most preferably at least about 7 MPa.

The composition may be coated onto substrates at useful thicknessesranging from 25-500 micrometers or more. Coating can be accomplished byany conventional means such as roller, dip, knife, or extrusion coating.Solutions of the curable composition may be used to facilitate coating.Stable thicknesses are necessary to maintain the desired coatingthickness prior to crosslinking of the composition to form thecrosslinked composition.

Useful substrates can be of any nature and composition, and can beinorganic or organic. Representative examples of useful substratesinclude ceramics, siliceous substrates including glass, metal, naturaland man-made stone, woven and nonwoven articles, polymeric materials,including thermoplastic and thermosets, (such aspolymethyl(meth)acrylate, polycarbonate, polystyrene, styrenecopolymers, such as styrene acrylonitrile copolymers, polyesters,polyethylene terephthalate), silicones, paints (such as those based onacrylic resins), powder coatings (such as polyurethane or hybrid powdercoatings), and wood; and composites of the foregoing materials.

The instant disclosure further provides a pressure sensitive adhesivewhich comprises a coating of the uncured or partially cured benzoxazinecomposition on a suitable substrate, such as an adhesive tape backing Apreferred method of preparing a pressure sensitive adhesive articlecomprises partially curing the novel composition to a useful coatingviscosity, coating the partially crosslinked composition onto asubstrate (such as a tape backing) and further curing the composition.Useful coating viscosities are generally in the range of 500 to 10,000cps.

Materials

XU3560™ benzoxazine isbis(3-phenyl-3,4-dihydro-2H,3-benzoxazinyl)isopropane, abisphenol-derived benzoxazine, available from Huntsman Corporation, TheWoodlands Tex. Jeffamines™ D230, D400, and D2000 are poly(oxyalkylenes)terminal diamines having molecular weights of about 230, 400 and 2000,respectively. Jeffamine™ T403 is a poly(oxyalkylenes) terminal triaminehaving molecular weights of about 403. All Jeffamines™ were obtainedfrom Huntsman Corporation.

PTMP (pentaerythritol tetrakis(3-mercaptopropionate), and TMMP(trimethylolpropane tris-3-mercaptonpropionate) were obtained from EvansChemetics LP, 33 Wood Avenue South Iselin N.J. 08830.

KarenzMT™ NR-1(1,3,5-Tris(3-melcaptobutyloxethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione)and KarenzMT™ PE1 (Pentaerythritol tetrakis(3-mercaptobutylate) wereobtained from Fine Chemicals Group, Specialty Chemicals Department,Showa Denko K.K., Tokyo, Japan

TMMP (trimethylolpropane tris-3-mercaptonpropionate) was obtained fromSC Organic Chemical Subsidiary, Sakai Chemical, Osaka, Japan.

PETG a terephtalate copolymer of polyethylene glycol andcyclohexanedimethanol), was obtained from Yodo Kagaku, Fukui, Japan

IOTGA (isooctyl ester of the thioglycolic acid) was obtained from TokyoKasei America Company, 9211 N. Harborgate Street, Portland, Oreg. 97203,U.S.A.

Paraformaldehyde was obtained from Aldrich Chemical Company, Milwaukee,Wis.

p-chlorothiophenol was obtained from Aldrich Chemical Company,Milwaukee, Wis.

Benzyl mercaptan was obtained from Aldrich Chemical Company, Milwaukee,Wis.

ortho-durene α-1,α-2 dithiol was obtained from Aldrich Chemical Company,Milwaukee, Wis.

SMS-042™-Mercaptopropyl)methylsiloxane-dimethylsiloxane copolymer wasobtained from Gelest, Inc., Morrisville, Pa.

Preparative Example 1-3 Benzoxazine A

A benzoxazine derived from a poly(ethylene oxide)diamine was prepared bycombining a mixture of D-400™ diamine (215 grams, 0.5 mol),paraformaldehyde (66 grams, 2.2 mol,) and phenol (94 grams, 1 mol,Aldrich) in a 2 L round bottom flask, equipped with a reflux condenser.To this was added approximately 300 ml of chloroform, then the mixturewas heated to a reflux for 10 hours. The reaction mixture was allowed tocool and the solvent and the water of condensation were removed underreduced pressure. The resulting product (approx 320 grams) was a veryviscous yellow liquid.

Using the same procedure Benzoxazines B and C were prepared from thediamine Jeffamine™ D230 and the triamine Jeffamine™ T403, respectively.

Example 1

To Benzoxazine A (0.666 grams, 0.001 mol), IOTGA (0.409 grams, 0.002mol) were added neat at room temperature and stirred in a metal cup. Thecharacteristic mercaptan odor disappeared immediately upon stirring. Analiquot of the thus obtained substance was dissolved in deuteratedchloroform (CDCl₃) and the ring opened structure, below, was confirmedby ¹H and ¹³C NMR.

Example 2

To XU3560™ bisphenol-A-based benzoxazine (0.462 grams, 0.001 mol) in ametal cup was added IOTGA, (0.409 grams, 0.002 mol,). The cup was placedonto a hotplate at 100° C. and stirred for approximately a minute as thebenzoxazine melted. The characteristic mercaptan odor disappearedimmediately upon stirring. An aliquot of product was dissolved indeuterated chloroform (CDCl₃) and the ring opened structure, below, wasconfirmed by ¹H and ¹³C NMR:

Example 3

To Benzoxazine A (3.33 g, 0.005 mol) heated at 100 C in a metal cup toreduce its viscosity, was added p-chlorothiophenol (1.44 g, 0.01 mol,Aldrich). The cup was placed onto a hotplate at 100 C and stirred forapproximately a minute as the thiophenol melted. The characteristicmercaptan odor disappeared immediately upon stirring. An aliquot of thussubstance produced was dissolved in deuterated chloroform (CDCl₃) andthe ring opened structure, below, was confirmed by ¹H and ¹³C NMR:

Example 4

To Benzoxazine A (3.33 grams, 0.005 mol) heated at 100 C in a metal cupto reduce its viscosity, was added benzyl mercaptan (1.24 grams, 0.01mol,). The cup was placed onto a hotplate at 100 C and stirred forapproximately a minute. The characteristic mercaptan odor disappearedimmediately upon stirring. An aliquot of thus substance produced wasdissolved in deuterated chloroform (CDCl₃) and the ring openedstructure, below, was confirmed by ¹H and ¹³C NMR

Example 5

To Benzoxazine A (3.33 grams, 0.005 moles) p-nitrothiophenol (1.55 g,0.01 mol) were added at room temperature and stirred. A dramatic colorchange from yellow to blood red wherever the two reactants come intocontact, and some viscosity increase was observed. To aid the mixing,the reaction mixture was then placed on a hot plate at 100 C. Thereaction yields a dark ruby red liquid. An aliquot of thus substanceproduced was dissolved in deuterated chloroform (CDCl₃) and the ringopened structure, below, was confirmed by ¹H and ¹³C NMR:

Example 6

2.68 grams of SMS-042(Mercaptopropyl)methylsiloxane-dimethylsiloxanecopolymer (Gelest) was added to Benzoxazine A (0.333 grams, 0.0005 mol)in a metal cup on a hotplate and heated at 100 C temperature whilestirring. The mixture phase separated producing an increasingly thickerand eventually rubbery, opaque yellowish mass.

Example 7

α-1, α-2 dithiol ortho-durene (0.816 grams, 0.00424 mol, 97% Aldrich)were added to XU3560™ bisphenol-A based benzoxazine (1.959 grams,0.00424 mol) in a 100 ml round bottom flask equipped with a condenserand dissolved in toluene. Two drops of acetic acid were added tocatalyze the reaction. The reaction was heated to reflux for 8 hours.The solvent was removed using a water azeotrope in a rotary evaporatorto yield yellowish-orange product. An aliquot was dissolved in warmdeuterated dimethyl sulfoxide (dmso-d6), and the ring opened polymericstructure, below, was confirmed by ¹H NMR. Another aliquot of thepolymer was partially soluble in dimethyl formamide (DMF). TheDMF-soluble fraction was analyzed using gel-permeation chromatography(GPS) to provide an approximate molecular weight Mw of 62,000 daltonsfor the soluble fraction.

Example 8

1.37 gram of 4-chloro 1,3 benzene dithiol (98%, 0.0079 mol, Aldrich) wasadded to a round bottom flask, equipped with a condenser, followed byapproximately 20 ml of toluene and XU-3560 bisphenol-A based benzoxazine(3.65 grams 0.0079 mol, Huntsman). Two drops of acetic acid were addedto catalyze the reaction. The flask was heated to reflux for 8 hourduring which the solution turned progressively darker yellow, and yellowprecipitate formed on the walls of the reaction flask. The solvent wasremoved using a water azeotrope in a rotary evaporator to yield a brightyellowish-orange product. An aliquot of the product was dissolved inwarm deuterated dimethyl sulfoxide (dmso-d6), and thus the ring openedpolymeric structure, below, was confirmed by ¹H NMR. Adimethylformamide-soluble fraction was analyzed using gel-permeationchromatography (GPS) to provide an approximate molecular weight Mw of10,000 daltons for the soluble fraction.

Example 9

Benzoxazine A (3.33 grams, 0.005 mol) was heated with 5.5 grams of waterin a metal cup on a hot plate at 100 C and stirred hot. The contentswere allowed to cool to room temperature and then PTMP (1.22 grams0.0025 mol) were added and stirred. The mixture thickened gelled inapproximately the same time (less than 1 minute) as without water underroom temperature conditions. The example illustrates that thebenzoxazine-thiol reaction can take place in presence of and even underwater without any apparent effect thereof on the polymerization.

Example 10

A 0.396 gram sample of the material prepared in Example 9 was placedinto a vial of water (approximately 10 ml). The vial was capped andplaced into a 95° C. oven for 24 hours. After 24 hours the sample wasextracted, paper towel dried and re-weighed. The new mass was found tobe 0.401 grams. After 12 hours in open air the mass equilibrated to0.395 grams. The example demonstrates that benzoxazine-thiol adducts areeffective moisture barriers.

Example 11

KarenzMT-NR1 (1.89 grams, 0.0033 mol) was admixed with XU-3560 (2.31grams, 0.005 mol) in a metal cup. Two drops of acetic acid were added,and the mixture was deposited in a rectangular silicone rubber mold,sandwiched between two silicone release liner coated PET sheets andpressed between glass plates. The mold consisted of 10˜1 mm thick sheetwith rectangular cutouts (approximately 5 mm wide×30 mm long) to preparesamples for the dynamic mechanical analysis.

The clamped construct was then placed in an oven at 130° C. for 30minutes. The assembly was then allowed to cool to room temperature.Shiny, transparent lemon-yellow samples was obtained. The samples werebrittle and glassy. Dynamic mechanical analysis was run in Seiko DMA intensile mode at the temperature range between −80 C and 300° C. Afterthe run was completed, the sample was removed, examined visually andrepositioned for the subsequent DMA run. Ultimately, the samples werecycled 4 times between −50 C and 220° C. with the heating rate of 2°C./min. The samples did not noticeably darken with each run, and remaintransparent. The traces of the loss tangent of the DMA scans are shownin FIG. 1.

Example 12

PETG (1.08 grams, 0.0025 mol) was admixed to Benzoxazine A (3.33 grams,0.005 mol) in a metal cup at room temperature. Upon stirring, themixture gels within 10 seconds. The resulting material was a translucentgrayish rubber, sticky to the touch. When placed into an oven at 130°C., the material lost some of its tack, but remained rubbery.

Example 13

50 grams of XU-3560 benzoxazine was admixed with 50 grams of BenzoxazineA in a metal can. The can was placed into an oven at 130° C. for 30minutes and stirred while cooling to form a melt solution of the twobenzoxazine compounds. 20 grams (0.073 mol benzoxazine equivalents) ofthat mixture was heated to ca. 70° C. and to it was added TMMP (9.752grams, 0.073 mol thiol equivalents). The characteristic mercaptan odordisappeared immediately upon stirring. Upon mixing the viscosity, whichinitially dropped, started to increase after approximately a minute ofmixing. An aliquot of the reaction product was dissolved in deuteratedchloroform and the ring opened structure was confirmed by IH and 13C NMRfor the aliphatic fraction derived from Benzoxazine A, while thearomatic fraction derived from benzoxazine XU-3560 of the benzoxazineappeared unreacted as NMR showed the oxazine ring still closed.

Example 14 Cohesive Strength Method Lap Shear Strength Testing

Lap shear specimens were made using 4″×7″×0.063″ 7075 T6 bare aluminumthat had been anodized according to Boeing Aircraft CompanySpecification BAC-5555. The anodization voltage was 22.5 volts. Thespecimen was generated as described in ASTM Specification D-1 002-05.

A strip of approximately Y;″×10 mils of the benzoxazine-thiol adduct,prepared in Example 13 was applied to one edge of each of the twoanodized aluminum adherends using a scraper. Three 5 mil diameter pianowires were used as spacers for bondline thickness control. The bond wasclosed and taped on the edge. The bond was placed between sheets ofaluminum foil and pieces of cardboard. Two 14# steel plates were used toapply pressure to provide for adhesive spreading. The assembly wasplaced into an oven heated to 130° C. for 1 hour. After the adhesive hadbeen allowed to cool to room temperature, the larger specimen was cutinto 1″ wide samples, providing a Y; square inch bonded area. Six lapshear samples were obtained from each larger specimen. The bonds weretested to failure at room temperature on a Sintech Tensile Testingmachine using a crosshead displacement rate of 0.1″/min. The failureload was recorded. The lap width was measured with a vernier caliper.The lap shear strengths are calculated as (2× failure load)/measuredwidth. The average and standard deviation were calculated from theresults of six tests. The lap shear strength was 2174 lbs/in2 (˜15MPa)-21-.

T-Peel Test Method

T-peel values were measured using 4″×8″×0.025″ 7075 T6 bare aluminumthat had been anodized as described above. The test was as described inASTM D-1876; Standard Test Method for Peel Resistance of Adhesives(T-Peel Test, “Annual Book of ASTM Standards, vol. 15.06, pp. 115-117(1995). A strip of approximately 2″×5″×10 mil of adhesive prepared inthe Example 13 was applied to both of the two anodized aluminumadherends. 10 mil thick spacers made from brass shims were applied tothe edges of the bonded area for bondline thickness control. The bondwas closed and adhesive tape was applied to hold the adherends 10together during the cure. The adhesive bonds were placed between sheetsof aluminum foil and also between pieces of cardboard. Four 14 poundsteel plates were used to apply pressure to provide for adhesivespreading. The assembly was placed into an oven heated to 130° C. for 1hour. After the adhesive had been allowed to cool to room temperature,the larger 15 specimen was cut into 1″ wide samples, yielding two 1″wide specimens. The bonds were tested to failure at room temperature ona Sintech Tensile Testing machine using a

crosshead displacement rate of 12″/min. The initial part of the loadingdata was ignored. The average load was measured after about 1″ waspeeled. The T-peel strength is the average of three peel measurementswas 2.2 lbf/in (3.8 N/cm).

Overlap Shear Strength

Overlap Shear Strength was determined using a maple wood substrate asfollows. A 0.5 gram (.+−.0.05 grams) quantity of the hot meltcomposition to be tested was preheated in a sealed cartridge at250.degree. F. (121.degree. C.) for between 30 and 60 minutes prior toextruding it onto one end portion of a 1 inch (2.5 cm) wide by 4 inch(10 cm) long by 0.31 inch (0.8 cm) thick section of a smooth maple woodpanel (available from Martin Lumber, St. Paul, Minn.). The woodsubstrate had been previously conditioned for 7 days at about 77.degree.F. (25.degree. C.) and 50% relative humidity. After the adhesive wasapplied, 0.003-0.005 inch (0.08-0.13 mm) diameter glass beads weresparingly sprinkled uniformly on the molten adhesive to control bondlinethickness. An overlap bond was then formed in the lengthwise directionby immediately mating the substrate with another piece of maple toprovide a 0.5 inch by 1.0 inch (1.25 by 2.5 cm) overlap bond area. Firmhand pressure was applied to compress the adhesive to a thickness of0.003-0.005 inches (0.08-0.13 mm) and to squeeze excess adhesive fromthe bond area. The test assembly was not moved for between 5 and 10minutes. Excess flash (if present) was trimmed from the bottom side ofthe assembly. At this point a bond had formed and the initial overlapshear strength was measured. The bonded substrates were allowed to cureat about 77.degree. F. (25.degree. C.) and 50% relative humidity forvarious periods of time before testing for overlap shear strength.

The resulting test coupon was tested for overlap shear strength at acrosshead speed of 2 inches/minute (5.1 centimeters/minute) using aSINTECH 10 Tensile Tester (available from MTS Systems Corporation, EdenPrairie, Minn.). Three test coupons were evaluated, the load valuesobtained were multiplied by 2 to normalize to a 1 square inch overlaparea, and an average value for overlap shear strength was calculated.The results are reported in pounds per square inch (psi) (MegaPascals,MPa). In one embodiment, a value of 1000 psi after 24 hours was desired.

Example 15

Benzoxazine composition employed in Example 13 was loaded with 17%silicone core shell toughener by Kaneka Texas Corporation. To 19.33grams (0.059 mol BZ) of that material TMMP was admixed (7.8 grams, 0.059mol thiol). The resulting material 25 was coated onto aluminum adherentsas in the previous Examples. The following adhesive data were obtained:

XU3560/JD400BZ/CST/TMMP Overlap Shear T-peel Average Value 1472 lbs/in25.2 lb/in STD 48 1.2

1. A B-stagable adhesive composition comprising: a) 30 to 90 mole % ofone or more N-aryl benzoxazines; b) 10 to 70 mole % of one or moreN-alkyl benzoxazines; c) a stoichiometric equivalent of one or morethiol compounds ±15%, relative to the benzoxazines, wherein the thiolcompound is of the formula R⁴—(S—H)_(n), wherein R⁴ is a non-polymericaliphatic, cycloaliphatic, aromatic or alkyl-substituted aromatic moietyhaving from 1 to 30 carbon atoms and optionally 1 to four catenaryheteroatoms of oxygen, nitrogen or sulfur; wherein the thiol compoundswill react with the N-alkyl benzoxazine to form a partially curedmixture at a first temperature then the N-aryl benzoxazine will reactwith the remaining thiol compounds to produce a fully cured adhesive ata second higher temperature; and which when cured has an overlap shearstrength of at least 0.5 MPa.
 2. An adhesive composition comprising: athermal reaction product of the composition of claim 1 formed by heatingthe composition to at least a first temperature.
 3. The adhesivecomposition of claim 2 wherein the thermal reaction product of thecomposition of claim 1 is capable of further thermal reaction uponheating to a second temperature, wherein the second temperature ishigher than the first temperature.
 4. The adhesive composition of claim1 wherein the polybenzoxazines are of the formula:

wherein each of R¹ is H or an alkyl group; R² is H, a covalent bond, ora polyvalent (hetero)hydrocarbyl group; R⁵ is a mixture of aromatic andaliphatic groups, and x is at least
 1. 5. The adhesive composition ofclaim 1 wherein the benzoxazines are of the formula:

wherein each of R¹ is H or an alkyl group; R² is H, a covalent bond, ora divalent (hetero)hydrocarbyl group; R⁵ is a mixture of aromatic andaliphatic groups.
 6. The adhesive composition of claim 1 wherein thebenzoxazines are of the formula:

each of R¹ is H or an alkyl group; R² is a covalent bond, or a divalent(hetero)hydrocarbyl group; R⁵ is a mixture of aromatic and aliphaticgroups.
 7. The adhesive composition of claim 1 wherein the benzoxazinesare of the formula:

wherein, each of R¹ is H or an alkyl group; R² is a covalent bond, or adivalent (hetero)hydrocarbyl group; R⁵ is a mixture of aromatic andaliphatic residues of a primary diamino compounds; and z is at least 2.8. The adhesive composition of claim 1 wherein the thiol compound is ofthe formula:R⁶—[(CO₂)_(x)—R⁷—SH]_(y), where R⁶ is an alkylene group, an aryl group,an oxyalkylene group, or combination thereof, R⁷ is a divalenthydrocarbyl group, x is 0 or 1, y is 1 to
 6. 9. The adhesive compositionof claim 1 wherein the thiol compound is of the formula:

wherein R⁶ is an alkylene group, an aryl group, an oxyalkylene group, orcombination thereof, R⁷ is a divalent hydrocarbyl group, x is 0 or 1, yis 1 to
 6. 10. The adhesive composition of claim 1 wherein the thiolcompound is of the formula:

wherein R⁶ is an alkylene group, an aryl group, an oxyalkylene group, orcombination thereof, R⁷ is a divalent hydrocarbyl group, x is 0 or 1, yis 1 to
 6. 11. The adhesive composition of claim 1 wherein the thiolcompound is of the formula:

wherein R⁶ is an alkylene group, an aryl group, an oxyalkylene group, orcombination thereof, R⁷ is a divalent hydrocarbyl group, y is 1 to 6.12. A method for assembly comprising: providing the adhesive compositionof claim 1; providing a substrate and an adherent; applying saidadhesive composition to one of said substrate and said adherent; heatingsaid applied adhesive composition to a first temperature; optionallycooling said adhesive composition; applying the other of said substrateand said adherent to said heated adhesive composition; and heating saidadhesive composition to a second temperature to further advance the cureof the adhesive composition, wherein the second temperature is higherthan the first temperature.
 13. A method for assembly comprising:providing the adhesive composition of claim 12; providing a substrateand an adherent; applying said adhesive composition to one of saidsubstrate and said adherent; applying the other of said substrate andsaid adherent to said heated adhesive composition; and heating saidadhesive composition to a second temperature to further advance the cureof the adhesive composition, wherein the second temperature is higherthan the first temperature.
 14. A method for assembly comprising:providing the adhesive composition of claim 1; providing a substrate andan adherent; applying said adhesive composition to one of said substrateand said adherent; heating said applied adhesive composition to a firsttemperature; applying the other of said substrate and said adherent tosaid heated adhesive composition; and continuing heating of saidadhesive composition to a second temperature, higher than the firsttemperature to further advance the cure of the adhesive composition.